Since Sir Charles Lyell published his most accurate and detailed paper “On the Tertiaries of Belgium and French Flanders,” geologists could only differ in their opinions on the facts mentioned by him, New discoveries have been made in Belgium only in the last few years; besides the splendid cuttings in the ditches for the fortification of Antwerp, about which I am going to speak afterwards, there has been found, near Mons, by sinking a well, a thick bed of lime and limestone at the base of all hitherto-known Belgian Teritiary beds, containing numerous and well-preserved Tertiary marine and fresh-water mollusca. The discoverers, MM. Cornet and Briart, Engineers of Mines, and most zealous geologists, described very carefully the geological position and afterwards the extension of these lowest Tertiary beds in Hainaut. In their first paper they had tried to determine the Molluscan fauna of this basement bed, after Deshayes' works; but, out of 150 species, they could name only 22, and amongst these there are still some very doubtful ones.